The present invention relates in general to battery chargers, and, more specifically, to an interface circuit for coupling energy from a solar panel to a battery to be recharged.
Rechargeable batteries are used as a power source in a wide variety of devices and machines and over a great range of voltages and storage capacities. The chemistries of conventional rechargeable batteries include lead-acid, nickel-cadmium, nickel metal-hydride, and lithium ion, among others. Each chemistry has a corresponding unique cell mid-point voltage. Particular batteries may use various combinations of cells, resulting in an ability to provide rechargeable batteries with many different terminal voltages.
Different rechargeable batteries have different requirements for an associated battery charger that can be used to deliver a charging current or voltage that most safely and effectively charges the battery. A recharge voltage must be provided that is greater than the terminal voltage of the rechargeable battery in order to reverse current through the battery during a charge cycle. On the other hand, battery damage may result if too high of a charging current is forced through the battery for too long of a time period. Chargers can also be used with battery chemistries not usually considered to be rechargeable, such as restoring charge to slightly used alkaline batteries. Thus, battery chargers are needed covering a wide variety of characteristics.
A charger can be made inexpensively to satisfy the charging requirements of one specific battery type, but no charger has met the specifications for charging very many different battery types without utilizing complicated and expensive circuits for performing voltage or current conversions and for monitoring battery charge cycles. Charger design also depends upon the power source being used. For example, a charger may be designed to utilize AC power from a fixed outlet of a power grid or DC power from a voltage generator such as a solar panel. Thus, typical chargers in the prior art are either designed for one specific input voltage or use complex circuits for adapting to different input voltages.